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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 26 (1988), S. 372-376 
    ISSN: 1612-1112
    Keywords: Size exclusion chromatography ; Lightscattering ; Calibration ; Axial dispersion ; Dispersion correction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new computational procedure for the simultaneous calibration of separation and axial dispersion by using SEC coupled with a LALLS detector is presented. Its performance is tested by SEC/LALLS experiments with commercially available samples of broad and narrow polystyrene standards. The peakbroadening parameters were calculated by a novel method which utilizes the different effects of axial dispersion on polymers with narrow and broad molecular weight distribution. The dispersion function was assumed to be gaussian. The variation of the dispersion parameter with molecular weight is in good agreement with reports in the literature. Experimental chromatograms have been corrected for the axial dispersion effect.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 47-55 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The peak broadening in size exclusion chromatography of seven commercial polystyrene (PS) standards with narrow molar mass distribution (MMD) and of 6-9 polypropylene (PP) fractions (M̄w/M̄n = 1.34-2.10) obtained by direct extraction was determined in four different column sets. The dependence of the Gaussian peak broadening parameter, σ2, on the peak elution volume was different for PS and PP. For a commercial grade of controlled rheology PP (CR-PP) (Daplen PT55) with M̄w/M̄n 〈 3 it was shown that disregard of the peak broadening effect leads to considerable errors in the MMD at low and higher molar mass and in the polydispersity parameter M̄w/M̄n. The same lot was studied in an Austrian National Research program for its physical propeties in processing and application and in a round-robin test of IUPAC working party IV.2.2. on molecular characterization of commercial polymers. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: A bleached spruce sulfite pulp is degraded by means of cellulase from T. reesei. During the reaction, degree of polymerization, crystallinity and void volume of the residue are studied. Only very minor changes are found. Furthermore, the molecular mass and hydrodynamic radius of the total enzyme, of its C1-fraction, and of the residual enzyme are determined. The enzyme molecule is considerably larger than the channels leading into the interior of cellulose. Therefore, a reaction mechanism of the “all or nothing” type is suggested.
    Notes: Ein gebleichter Fichtensulfitzellstoff wird mit Cellulase aus T. reesei abgebaut. Während der Reaktion werden Polymerisationsgrad, Kristallinität und Hohlraumvolumen des Rückstandes untersucht. Es werden nur sehr geringfügige Änderungen gefunden. Weiter werden am Gesamtenzym, einer daraus isolierten C1-Fraktion sowie dem Restenzym Molekülmasse und hydrodynamischer Radius bestimmt. Das Enzym-Molekül ist wesentlich größer als die Kanäle, die in das Innere der Cellulose führen. Es wird daher ein Reaktionsmechanismus vom „alles oder nichts“ -Typ vorgeschlagen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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